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AFE4300 output VLDO going down to zero

Rahul Kidecha
Prodigy 10 points
Other Parts Discussed in Thread: AFE4300

Hi,

i am using AFE4300 to design wireless Weight scale with body mass composition.

i integrated AFE with nrf successful but after some time VLDO (this pin supply 1.7 to power resistance bridge)voltage going down to zero from 1.7 volt.

can you guide me to solve this issue?

Regards,

Rahul Kidecha

  • +1
    TI__Mastermind 49746 points

    Hi Rahul,

    Can you find the test conditions when the VLDO starts to drop?

    Is there any register read access? Are the supplies stable? What is the status of RST pin?

    Do you see this issue on the AFE4300 EVM?

  • 0 in reply to Praveen Aroul
    Prodigy 10 points

    Hi Praveen,

    Praveen Aroul said:
    What is the status of RST pin?

    We were using RST_MCU pin to reset AFE4300 before write value into register. But I disconnected pin and it is working fine. I believe reset pin was creating issue.
    Do we need to give reset plus to AFE4300 before initialization or writing value into register?

    but I was getting some offset value instead of zero (No Weight condition).

    can you guide me how to set OFFSET_DAC_VALUE in WEIGHT_SCALE_CONTROL register if offset value is A9 (in hex)?

    Praveen Aroul said:
    Is there any register read access?

    I am using below value to configure AFE4300 to use as weight scale.

    void afe_init()
    {
    write_reg(ADC_CONTROL_REGISTER1, 0x41, 0x50); // SPS
    write_reg(MISC_REGISTER1, 0x00, 0x00);
    write_reg(MISC_REGISTER2, 0xFF, 0xFF);
    write_reg(DEVICE_CONTROL1, 0x60, 0x05); // turn on weight scale chain
    write_reg(ISW_MUX, 0x00, 0x00); //0x08, 0x04);
    write_reg(VSENSE_MUX, 0x00, 0x00); //0x08, 0x04);
    write_reg(IQ_MODE_ENABLE, 0x00, 0x00);
    write_reg(WEIGHT_SCALE_CONTROL, 0x00, 0x00); // gain = 1, slight offset correction
    write_reg(BCM_DAC_FREQ, 0x00, 0x00);
    write_reg(DEVICE_CONTROL2, 0x00, 0x00);
    write_reg(ADC_CONTROL_REGISTER2, 0x00, 0x00);
    write_reg(MISC_REGISTER3, 0x00, 0x30);
    }

    after writing these value when I am reading again those registers. And reading from ADC_DATA_RESULT register getting some constant value and not changing even i put weight.

    When we read register does it change the register value?

    Thank You.

    Rahul Kidecha

  • 0 in reply to Rahul Kidecha
    TI__Mastermind 49746 points

    Hi Rahul,

    Yes, after power up, the device must be reset to set all internal registers to their default state. Reset signal should be an active low pulse. Please refer to section 9.1 in the datasheet for power up and initialization sequence.

    Regarding the register read, every time a register is read, the register must be rewritten, except when reading the data output register.

    You may want to check your load cell connection to the AFE weigh scale channel inputs.